Fixedband

Fixedband, sometimes written fixed-band, is a term used in radio communications and signal processing to describe hardware and systems that operate within a fixed, preselected portion of the radio spectrum. In a fixedband design, the center frequency and channel bandwidth are hard-coded or set during manufacture and are not intended to be altered by the user. This contrasts with tunable or software-defined systems that can access multiple bands or adjust parameters across a broader range.

Operating principles: Fixedband receivers and transceivers use fixed high-Q filters matched to their designated band, with a stable local oscillator configured for a specific frequency. The front-end, mixer, and intermediate-frequency stages are optimized for minimal drift within the band, with limited or no automatic tuning range. This simplifies design, reduces cost, and can improve reliability in environments with strict channel plans and interference constraints. Compliance with regulatory spectrum use is typically achieved by reserving a dedicated band and controlled channel spacing.

Applications: Fixedband devices are common in mission-critical or industrial contexts where predictable performance is required, such as fixed wireless access links, public safety and industrial two-way radios, telemetry, and some point-to-point or broadcast links. They are favored where spectrum is scarce, channels are tightly managed, or where cost and robustness take priority over flexibility.

Advantages and limitations: The fixed nature of the band offers simplicity, lower component count, and easier certification, along with potential improvements in stability and noise performance within the band. However, lack of frequency agility limits interoperability, future-proofing, and adaptability to changing spectrum allocations. If a system must operate across multiple bands, a tunable or software-defined alternative may be preferred.